Operating Revenue (Schedule of Operating Revenue) (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Public Utilities General Disclosures [Line Items]
Operating revenue from contracts with customers	$ 3,524	$ 3,452
Renewable Energy Investment Tax Credits
Public Utilities General Disclosures [Line Items]
Operating revenue from contracts with customers	5	5
Alternative Revenue Programs
Public Utilities General Disclosures [Line Items]
Other revenues	28	28
Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Operating revenue from contracts with customers	2,417	2,346
Virginia Electric and Power Company | Renewable Energy Investment Tax Credits
Public Utilities General Disclosures [Line Items]
Operating revenue from contracts with customers	2	3
Virginia Electric and Power Company | Alternative Revenue Programs
Public Utilities General Disclosures [Line Items]
Other revenues	$ 27	$ 27